'\" t
.\"     Title: limits.conf
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets v1.79.2 <http://docbook.sf.net/>
.\"      Date: 10/24/2024
.\"    Manual: Linux-PAM Manual
.\"    Source: Linux-PAM
.\"  Language: English
.\"
.TH "LIMITS\&.CONF" "5" "10/24/2024" "Linux\-PAM" "Linux\-PAM Manual"
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.el       .ds Aq '
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.nh
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.SH "NAME"
limits.conf \- configuration file for the pam_limits module
.SH "DESCRIPTION"
.PP
The
\fIpam_limits\&.so\fR
module applies ulimit limits, nice priority and number of simultaneous login sessions limit to user login sessions\&. This description of the configuration file syntax applies to the
/etc/security/limits\&.conf
file and
*\&.conf
files in the
/etc/security/limits\&.d
directory\&.
.PP
The syntax of the lines is as follows:
.PP
\fI<domain>\fR
\fI<type>\fR
\fI<item>\fR
\fI<value>\fR
.PP
The fields listed above should be filled as follows:
.PP
<domain>
.RS 4
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
a username
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
a groupname, with
\fB@group\fR
syntax\&. This should not be confused with netgroups\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
the wildcard
\fB*\fR, for default entry\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
the wildcard
\fB%\fR, for maxlogins limit only, can also be used with
\fB%group\fR
syntax\&. If the
\fB%\fR
wildcard is used alone it is identical to using
\fB*\fR
with maxsyslogins limit\&. With a group specified after
\fB%\fR
it limits the total number of logins of all users that are member of the group\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
an uid range specified as
\fI<min_uid>\fR\fB:\fR\fI<max_uid>\fR\&. If min_uid is omitted, the match is exact for the max_uid\&. If max_uid is omitted, all uids greater than or equal min_uid match\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
a gid range specified as
\fB@\fR\fI<min_gid>\fR\fB:\fR\fI<max_gid>\fR\&. If min_gid is omitted, the match is exact for the max_gid\&. If max_gid is omitted, all gids greater than or equal min_gid match\&. For the exact match all groups including the user\*(Aqs supplementary groups are examined\&. For the range matches only the user\*(Aqs primary group is examined\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
a gid specified as
\fB%:\fR\fI<gid>\fR
applicable to maxlogins limit only\&. It limits the total number of logins of all users that are member of the group with the specified gid\&.
.RE
.RE
.PP
<type>
.RS 4
.PP
hard
.RS 4
for enforcing
\fBhard\fR
resource limits\&. These limits are set by the superuser and enforced by the Kernel\&. Users cannot raise their own requirement of system resources above such values\&.
.RE
.PP
soft
.RS 4
for enforcing
\fBsoft\fR
resource limits\&. These limits are ones that the user can move up or down within the permitted range by any pre\-existing
\fBhard\fR
limits\&. The values specified with this token can be thought of as
\fIdefault\fR
values, for normal system usage\&.
.RE
.PP
\-
.RS 4
for enforcing both
\fBsoft\fR
and
\fBhard\fR
resource limits together\&.
.sp
Note, if you specify a type of \*(Aq\-\*(Aq but neglect to supply the item and value fields then the module will never enforce any limits on the specified user/group etc\&. \&.
.RE
.RE
.PP
<item>
.RS 4
.PP
core
.RS 4
limits the core file size (KB)
.RE
.PP
data
.RS 4
maximum data size (KB)
.RE
.PP
fsize
.RS 4
maximum filesize (KB)
.RE
.PP
memlock
.RS 4
maximum locked\-in\-memory address space (KB)
.RE
.PP
nofile
.RS 4
maximum number of open file descriptors
.RE
.PP
rss
.RS 4
maximum resident set size (KB) (Ignored in Linux 2\&.4\&.30 and higher)
.RE
.PP
stack
.RS 4
maximum stack size (KB)
.RE
.PP
cpu
.RS 4
maximum CPU time (minutes)
.RE
.PP
nproc
.RS 4
maximum number of processes
.RE
.PP
as
.RS 4
address space limit (KB)
.RE
.PP
maxlogins
.RS 4
maximum number of logins for this user (this limit does not apply to user with
\fIuid=0\fR)
.RE
.PP
maxsyslogins
.RS 4
maximum number of all logins on system; user is not allowed to log\-in if total number of all user logins is greater than specified number (this limit does not apply to user with
\fIuid=0\fR)
.RE
.PP
nonewprivs
.RS 4
value of 0 or 1; if set to 1 disables acquiring new privileges by invoking prctl(PR_SET_NO_NEW_PRIVS)
.RE
.PP
priority
.RS 4
the priority to run user process with (negative values boost process priority)
.RE
.PP
locks
.RS 4
maximum locked files (Linux 2\&.4 and higher)
.RE
.PP
sigpending
.RS 4
maximum number of pending signals (Linux 2\&.6 and higher)
.RE
.PP
msgqueue
.RS 4
maximum memory used by POSIX message queues (bytes) (Linux 2\&.6 and higher)
.RE
.PP
nice
.RS 4
maximum nice priority allowed to raise to (Linux 2\&.6\&.12 and higher) values: [\-20,19]
.RE
.PP
rtprio
.RS 4
maximum realtime priority allowed for non\-privileged processes (Linux 2\&.6\&.12 and higher)
.RE
.RE
.PP
All items support the values
\fI\-1\fR,
\fIunlimited\fR
or
\fIinfinity\fR
indicating no limit, except for
\fBpriority\fR,
\fBnice\fR, and
\fBnonewprivs\fR\&. If
\fBnofile\fR
is to be set to one of these values, it will be set to the contents of /proc/sys/fs/nr_open instead (see setrlimit(3))\&.
.PP
If a hard limit or soft limit of a resource is set to a valid value, but outside of the supported range of the local system, the system may reject the new limit or unexpected behavior may occur\&. If the control value
\fIrequired\fR
is used, the module will reject the login if a limit could not be set\&.
.PP
In general, individual limits have priority over group limits, so if you impose no limits for
\fIadmin\fR
group, but one of the members in this group have a limits line, the user will have its limits set according to this line\&.
.PP
Also, please note that all limit settings are set
\fIper login\fR\&. They are not global, nor are they permanent; existing only for the duration of the session\&. One exception is the
\fImaxlogin\fR
option, this one is system wide\&. But there is a race, concurrent logins at the same time will not always be detect as such but only counted as one\&.
.PP
In the
\fIlimits\fR
configuration file, the \*(Aq\fB#\fR\*(Aq character introduces a comment \- after which the rest of the line is ignored\&.
.PP
The pam_limits module does report configuration problems found in its configuration file and errors via
\fBsyslog\fR(3)\&.
.SH "EXAMPLES"
.PP
These are some example lines which might be specified in
/etc/security/limits\&.conf\&.
.sp
.if n \{\
.RS 4
.\}
.nf
*               soft    core            0
*               hard    nofile          512
@student        hard    nproc           20
@faculty        soft    nproc           20
@faculty        hard    nproc           50
ftp             hard    nproc           0
@student        \-       maxlogins       4
@student        \-       nonewprivs      1
:123            hard    cpu             5000
@500:           soft    cpu             10000
600:700         hard    locks           10
    
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.PP
\fBpam_limits\fR(8),
\fBpam.d\fR(5),
\fBpam\fR(8),
\fBgetrlimit\fR(2),
\fBgetrlimit\fR(3p)
.SH "AUTHOR"
.PP
pam_limits was initially written by Cristian Gafton <gafton@redhat\&.com>
